Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$117.78	5.546%	$124.3121	$124.31	$124.30	$124.30
Purchase #2	$94.31	4.758%	$98.7973	$98.80	$98.80	$98.80
Purchase #3	$90.76	6.756%	$96.8917	$96.89	$96.90	$96.90
Purchase #4	$20.50	7.803%	$22.0996	$22.10	$22.10	$22.10
Purchase #5	$218.31	12.605%	$245.828	$245.83	$245.85	$245.80
Purchase #6	$153.84	13.111%	$174.01	$174.01	$174.00	$174.00
Purchase #7	$127.45	13.285%	$144.3817	$144.38	$144.40	$144.40
7 purchase totals =	$822.95		$906.3204	$906.32	$906.35	$906.30